Outbreak of Murine Typhus -- Texas

A cluster of cases of murine (endemic) typhus has been reported
from Texas. From October 25 to November 11, 1982, five persons
became
ill with fever (temperature greater than or equal to 40C ( greater
than or equal to 104F)) (all five patients), headache (three
patients), and myalgia (two patients). On the 4th or 5th day of
illness, three patients developed a macular rash that began on the
trunk and spread to the extremities. Blood specimens obtained on
December 16, 1982, from three patients demonstrated indirect
fluorescent antibody titers of 1:512 or greater to typhus-group
rickettsiae; cross-absorption studies performed at CDC using
antigens
to Rickettsia typhi (the causative organism of endemic typhus) and
R.
prowazekii (the causative organism of epidemic typhus) indicated
the
former as the cause of the elevated titers. No serum specimens
were
obtained from the other two patients. Four patients received
appropriate antimicrobial therapy with tetracycline; all five
recovered without sequelae.

Three patients--a 27-year-old male, a 25-year-old female, and a
6-year-old female--lived in a house that had been unoccupied for 5
years before being moved in July 1982 to its present site on a
peanut
farm in Comanche County in northcentral Texas. The other two cases
occurred in a 24-year-old female who visited this family at their
home
every 1 or 2 weeks and a 48-year-old female, the grandmother of the
6-year-old, who lived one-quarter mile away and visited the house
at
least once a month. Inspection of the house revealed holes in the
roof, walls, and floors, and a large space beneath the house.
Family
members had heard rodents in the attic before the outbreak, and a
mouse had recently been killed in the bathroom. Two or 3 weeks
before
the outbreak, rat poison had been placed inside the house. Five
cats,
present in the home before the outbreak, died during the outbreak
period, four of unexplained causes, one in an accident. The cats
slept indoors and had fleas. The family also owned three dogs,
which
usually slept underneath the house; they remained healthy during
the
outbreak period. None of the patients recalled being bitten by
fleas.

An exterminator visited the house on November 19, 1982, and
applied insecticide and rat poison. No further illnesses among
family
members or visitors to the house have been reported.
Reported by T Ford, Region 4, CR Webb, Jr, MD, State
Epidemiologist,
Texas Dept of Health; Div of Viral Diseases, Center for Infectious
Diseases, CDC.

Editorial Note

Editorial Note: The causative agent of murine typhus--R. typhi
(formerly R. mooseri) is maintained in nature by commensal rats and
their ectoparasites. Humans acquire the infection through contact
with the infected rat flea, Xenopsylla cheopis. The flea defecates
while feeding, and irritation from the bite causes the host to
scratch
and thus deposit rickettsiae from the feces into the wound. Other
mammals and ectoparasites, including cats and cat fleas, have been
found infected with R. typhi, although these infections, as well as
those in humans, are not important in maintaining the agent in
nature.

In the early 1940's, 2,000-5,000 cases of murine typhus were
reported annually in the United States, most in the Southeastern
and
Gulf Coast states. Incidence of the disease declined when rat
control
programs were instituted after World War II. Currently, murine
typhus
is not reportable in most states, and only 60-80 cases are reported
annually to CDC. In recent years, approximately 80% of these cases
have been reported from Texas. In 1981, the most recent year for
which information is available, Texas reported 49 cases of murine
typhus, with treatment information available for 43; 39 (91%)
patients
received appropriate therapy with tetracycline or chloramphenicol.
There were no deaths.

Although much information concerning the ecology of murine
typhus
is available (1), unresolved issues remain. In this outbreak, for
example, whether the cats or their fleas were involved in
transmitting
typhus to humans, whether they were uninvolved but also acquired
infection, or whether their deaths were entirely unrelated to the
outbreak could not be determined. (Dogs and dog fleas have not
been
found to harbor R. typhi.) Prompt reporting and investigation of
similar outbreaks in the future might help resolve such issues.

The use of rat poison in the home 2-3 weeks before the outbreak
may have precipitated the human illnesses. Rat fleas will seek
alternative hosts when rodents are not available and thus may
transmit
the disease to man. In areas where murine typhus is known to
occur,
rat control programs should be preceded by applying insecticides to
control these ectoparasites.

Reference

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